Rongeurs are medical devices that are typically used to remove bone and other tissue (e.g., cartilage) from a surgical site during a surgical procedure. Rongeurs of varying types and constructions are well known in the art.
Looking first at FIGS. 1-12, there is shown a typical prior art rongeur 5. Rongeur 5 comprises a bottom shaft 10 and a top shaft 15.
Bottom shaft 10 (FIGS. 1-5 and 9-12) generally comprises an elongated rigid shank having a proximal end 16 (FIG. 1) and a distal end 17 (FIG. 1). Bottom shaft 10 comprises a substantially flat upper surface 20 and terminates in a footplate 25 at the distal end of the shaft. Footplate 25 typically extends at a moderate obtuse angle with respect to the plane of upper surface 20. The proximal end of bottom shaft 10 typically terminates in a handle 30 (FIG. 1), which may be formed integral with bottom shaft 10 or may be otherwise connected thereto.
Top shaft 15 (FIGS. 1, 2, 6-12) generally comprises an elongated rigid shank having a proximal end 31 (FIG. 1) and a distal end 32 (FIG. 1). Top shaft 15 comprises a substantially flat bottom surface 35 and terminates in a concave surface 40 at the distal end of the shaft. Concave surface 40 is configured such that the edges of the distal end of the top shaft form a cutting edge 45 when top shaft 15 is applied against footplate 25 of bottom shaft 10. The proximal end of top shaft 15 is typically connected to a lever 50 (FIG. 1), which in turn is spring-biased away from handle 30, as will hereinafter be discussed in further detail.
Bottom shaft 10 further comprises a groove 55. Groove 55 is characterized by a wider proximal recess 60 and a narrower distal recess 65. Narrower distal recess 65 comprises an undercut 70.
Top shaft 15 further comprises a tongue 75 extending from bottom surface 35. Tongue 75 is characterized by a crossbar 80 which is connected to bottom surface 35 by a vertical riser 85. Tongue 75 of top shaft is sized to be slidably received in groove 55 of bottom shaft 10, whereby to form a T-slide connection.
Bottom shaft 10 and top shaft 15 are assembled together so that bottom surface 35 of top shaft 15 slides against top surface 20 of bottom shaft 10 and tongue 75 of top shaft 15 is slidably disposed in groove 55 of bottom shaft 10. This construction allows top shaft 15 to reciprocate longitudinally relative to bottom shaft 10 while remaining substantially parallel to, and in sliding engagement with, one another when top shaft 15 moves between (i) a resting position (i.e., where cutting edge 45 of top shaft 15 is spaced from footplate 25 of bottom shaft 10, as shown in FIGS. 1, 2 and 11), and (ii) a cutting position (i.e., where cutting edge 45 of top shaft 15 is in engagement with footplate 25 of bottom shaft 10, as shown in FIG. 12).
The reciprocating movement of top shaft 15 relative to bottom shaft 10 is typically effected by moving lever 50 (FIG. 1) proximally towards handle 30. More particularly, by virtue of the connection between top shaft 15 and lever 50, movement of lever 50 proximally causes top shaft 15 to slide distally relative to bottom shaft 10.
Preferably, springs 90 extend between handle 30 and lever 50 so that handle 30 and lever 50 remain separated from one another when rongeur 5 is in its resting (i.e., non-cutting) position (FIGS. 1, 2 and 11).
In use, the distal portion of rongeur 5 is deployed at a surgical site. Tissue targeted for removal is disposed between cutting edge 45 and footplate 25. Lever 50 is pulled proximally towards handle 30, which causes top shaft 15 to move distally along bottom shaft 10 until cutting edge 45 is brought into contact with footplate 25 (FIG. 12), thereby cutting the tissue disposed between cutting edge 45 and footplate 25. After cutting, lever 50 is released and top shaft 15 returns to its resting position (FIGS. 1, 2 and 11).
During use of rongeur 5, as top shaft 15 reciprocates relative to bottom shaft 10, top shaft 15 and bottom shaft 10 are kept in close vertical and horizontal alignment with each other as a result of the T-slide (i.e., tongue-and-groove) construction described above, with bottom surface 35 of top shaft 15 sliding along top surface 20 of bottom shaft 10. As top shaft 15 advances relative to bottom shaft 10, the distal movement of tongue 75 within groove 55 moves the proximal portion of tongue 75 from wider recess 60 into narrower recess 65. As this occurs, the volume of groove 55 which is disposed proximal to moving tongue 75 increases as tongue 75 moves distally. Inasmuch as bottom surface 35 of top shaft 15 makes a close sliding fit with top surface 20 of bottom shaft 10, this distal motion of tongue 75 creates a substantial suction force in the space proximal to the moving tongue, i.e., in wider recess 60. The result of this suction is that bone fragments, tissue debris and other bio-matter are drawn into wider recess 60, where they can collect and migrate to other portions of groove 55.
Unfortunately, it is difficult to remove bio-matter that collects in wider recess 60 without undertaking a time-consuming and uneconomical disassembly of rongeur 5. However, unless wider recess 60 and the rest of the rongeur can be effectively cleaned, the rongeur should not be used again because of the risk of contamination and spreading of pathogens. However, one-time use of an expensive piece of surgical equipment is undesirable at best, and effectively impractical with rongeurs.
As a result, one object of the present invention is to provide a novel rongeur that eliminates the suction force resulting from the movement of tongue 75 into narrower recess 65 so as to prevent the collection of bio-matter and other debris in wider recess 60 of bottom shaft 10 of rongeur 5.
An additional problem associated with prior art rongeurs is that the formation of groove 55 in general, and the formation of undercut 70 along narrower recess 65 in particular, tends to weaken the distal portion of bottom shaft 10 because it requires the removal of a substantial amount of the material that makes up the distal portion of bottom shaft 10 (e.g., metal). This is a particular problem as users of rongeurs frequently apply a substantial amount of force when actuating the device in order to cut tough tissue, which can cause the distal portion of bottom shaft 10 to bend during use, as inclined cutting edge 45 exerts a significant force against inclined footplate 25. See FIG. 12A. Such bending can substantially impair the efficiency and effectiveness of prior art rongeurs.
Accordingly, another object of the present invention is to provide for a strengthened rongeur.